Crochet decreases are used to make the fabric get smaller/narrower, and also to help create interesting stitch patterns. Two of the most common decreases you'll see are sc2tog (single crochet two together) and dc2tog (double crochet two together).
This technique is the same as the stitches get taller (e.g. trc2tog), and as more stitches are added to the decrease (e.g. dc3tog) - start each stitch, stopping before you pull through the last 2 loops, and then yarn over and pull through all the remaining loops on the hook. You can do it!
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